1. Field of the Invention
The present invention relates to a solid-liquid separator using a roller system, equipped with rollers each having a screen formed in the outer periphery thereof with plural pores, for separating a solid-liquid mixture into a solid substance and a liquid substance via the plural pores.
2. Description of the Prior Art
There has heretofore been known a solid-liquid mixture separator for separating liquid through filtration, squeezing and dehydration from a solid-liquid mixture having a solid substance and a liquid substance mixed with each other, in which cited as the solid-liquid mixture is a solid-liquid mixture (so-called “boiled soybean-water slurry” that is hereinafter referred to also as “soybean soup” in the description) as obtained through boiling of soybean slurry (so-called unheated soybean-water slurry) that has been acquired by immersing soybeans in water overnight and then scrubbing and crushing the soybeans while being added with water when manufacturing tofu, fried bean curd or soymilk beverage.
As a separator for a solid-liquid mixture, there are a screw-system one comprising a cylindrical screen having plural pores formed therein and a spiral screw driven and rotated within the cylindrical screen and a multistage-system one comprising the screw-system one and a cylindrical screen that has plural pores formed therein for gravity filtration (a screen for filtration) (Japanese Patent No. 3417794 or 3392322, for example). On the other hand, there is a roller-system one in which a solid-liquid mixture is supplied between a pair of right and left rollers facing each other, with their respective axial directions kept in parallel. Japanese Patent No. 3537377 (hereinafter referred to as “Citation 3”) points out that one extraction can only be attained with the pair of hollow rollers and performs squeezing with the pair of rollers (primary extraction) the solid-liquid mixture (soybean soup) supplied from above the pair of rollers and squeezing, with the lower surfaces of the rollers and a retention portion (secondary extraction), okara received on the retention portion with which an extraction passageway formed so that the amount to be discharged may be smaller than the amount to be received communicates. In the embodiment of Citation 3, as shown in FIG. 12, the retention portion 5 for okara (a solid substance) is formed so as to be surrounded by the pair of rollers 1, scrapers 4 for scraping the solid component adhering to the rollers, and opposing lower side surface portions 16a extending from opposing central portions 17 of the rollers 1 to the scrapers 4 and, at this retention portion 5, a throttle passageway 50 having a passageway throttled so that the amount to be discharged may be smaller than the amount to be received for giving squeezing pressure to the retained okara is formed. Incidentally, the throttle passageway 50 has a discharge outlet 51 provided with a lid body 53 biased with a spring 52 in the direction of closing the discharge outlet 51. The lid body 53 enables the opening area of the discharge outlet 51 to be varied in accordance with the internal pressure of the retention portion 5.
However, since the roller of the conventional solid-liquid separator using the roller system has a hollow interior and has a structure in which air is difficult to deaerate, pressure (load) of the liquid substance is insufficiently exerted on the screen (stiff load is exerted on the screen). Therefore, when pressure (load) has strongly been exerted on the screen, with the amount of the supplied liquid substance increased, problems of passing minute solid substances through the screen and generating foams inside the screen in a state of foams retained are entailed. This is further described citing an example in which soybean soup (unheated soybean-water slurry, boiled soybean-water slurry) is separated (filtered, dehydrated and squeezed) into soymilk and okara. When the roller is hollow, load of the soymilk is insufficiently exerted on the screen and, when load has strongly been exerted on the screen, with the amount of the supplied liquid substance increased, problems of passing residue through the screen, generating foams inside the screen in a state of foams retained and covering and clogging the screen with bean curd skin (the skin of soybean milk) are entailed. Ordinary soybean soup has minute foams admixed therein at all times and the inside of the screen is always in a state having air retained. Furthermore, even when residue or bean curd skin has adhered to the screen, a problem of providing the apparatus with no means for removing the same is entailed.
As is readable from the shape of a supply inlet 30 shown in FIG. 1 of Citation 3, since paired right and left rollers are used to adjust the amount of the solid-liquid mixture to be supplied mainly by means of its own weight from the above side, it can be inferred that it is difficult to adjust the supplied amount under the influence of the level or the density and viscosity of the solid-liquid mixture within the supply inlet and perform fluid filtration. That is to say, when separating soybean soup (unheated soybean-water slurry, boiled soybean-water slurry) into soymilk and okara, it is desirable to suppress retention of air. However, it is impossible to suppress the retention of air less than a constant amount. It is a matter of course that this is not applicable to a producing method in the absence of a defoaming agent, in which no defoaming agent is used. In addition, the conventional apparatus has a structure incapable of readily disassemble and clean itself and, therefore, does not satisfy the conditions required for food machinery. Moreover, it entails the problems of poor cleaning efficiencies in spite of using a large amount of cleaning liquid and inside retention of a large amount of cleaning liquid and residue.
In view of the above, the object of the present invention is to provide a solid-liquid separator using a roller system, in which a liquid substance is smoothly discharged out through the disposition of an inside drum within a roller and formation of a passageway for the liquid substance between the inside drum and the inside of a screen, the coefficient of discharging retained air and foams is heightened through an increase of the discharging flow rate and, at the same time, the cleaning coefficient is heightened through an increase of the flow rate of a detergent when cleaning the environment. Another object of the present invention is to provide a solid-liquid separator using a roller system, which is capable of filtering the screen under balanced pressure and extracting the liquid substance having suppressed the retention of air and regeneration of foams by the air retention.